Delamination effects in fuselage crack patching
The use of bonded composite patches in the repair of fatigue-damaged metallic aircraft structures has slowly gained broader acceptance in the past decade. Thick, highly-loaded structures have been successfully repaired with boronlepoxy on the F-111, B-1B, C-141B, and many other aircraft. Other materials, including lower modulus glass fiber/aluminum laminates, are also being implemented in fuselage (thin-skinned) structural repairs. The effects of typical bond line defects such as delaminations have been studied with the goal of quantifying the degradation in fatigue life of bonded repairs. Artificial delaminations in various locations were tested in bonded boron/epoxy and fiber metal laminate patches. Room temperature, constant amplitude fatigue experiments were performed on center-cracked 2024-T3 aluminum sheets repaired with adhesively bonded glass fiber/epoxy/ aluminum laminate and boron/epoxy patches. These specimens contained artificial delaminations covering 20 per cent of the total bonded area. Delamination size and growth were monitored ultrasonically, while crack growth was measured visually. Most repairs experienced accelerated crack growth in the presence of delaminations, and bond defects in the line of the pre-crack had the largest detrimental influence. The data provide a starting point for defining bonded repair inspection intervals when bond line defects are present.
- OSTI ID:
- 412078
- Report Number(s):
- CONF-960310--
- Country of Publication:
- United States
- Language:
- English
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